The present invention relates to hardware for connected reinforcement bars (i.e., rebars) to each other, and more particularly to hardware for connecting metallic rebars, fiber-reinforced polymer rebars, and/or other rebars, to each other.
Reinforced concrete is concrete in which rebars or fibers have been incorporated to strengthen the otherwise brittle concrete. Rebar is commonly made of carbon steel which is typically unfinished, but can be epoxy-coated, galvanized, or clad in stainless steel for use in corrosive environments. Fiber-reinforced polymer rebar is now also being used in high-corrosive environments. Without the added tensile strength provided by the rebars, many concrete structures would not be possible. Numerous structures and building components consist of reinforced concrete including: roads, bridges, slabs, walls, beams, columns, foundations, frames, and floor systems.
Reinforced concrete is often classified in two categories: pre-cast concrete and cast-in-place (or in-situ) concrete. Pre-cast concrete, which continues to grow in popularity, is formed in a controlled environment and then transported to the construction site and put in place. Conversely, cast-in-place concrete is poured-in-place into forms which are constructed on site, and then allowed to cure. The advantages of pre-cast concrete include improved material quality when formed in controlled conditions and the reduced cost and time of constructing forms for use with cast-in-place concrete. However, integrating and/or connecting pre-cast components require a reinforcement bar from each component to be connected together. Current splicing techniques include: welding, rebar overlap, or cast-iron connectors.
Pre-cast concrete structures provide significant advantages over cast-in-place structures, specifically in their ability to reduce construction times required; thus, reducing the overall cost of the structures. The significant disadvantage of precast concrete structures is in how to connect the precast members in a safe and efficient manner. Many pre-cast members used in construction are currently jointed by spliced steel reinforcing bars. These connections are susceptible to corrosion which could lead to deterioration of the strength of the structure. The primary cause of corrosion in steel joint connects is exposure to sodium chloride that is present in marine environments or de-icing salts that are applied to bridge decks and parking structures. Some steel bar splice couplers include NMB Splice-Sleeve® products, available from Splice Sleeve North America of Irvine Calif., and others. However, steel connectors, like cast-iron rebar connectors and all other metallic rebar connectors, can be rather heavy and bulky. Workers on jobsites are required to physically manipulate these heavy and bulky connectors while aligning pairs of rebar to be connected. This can, at times, prove tiring and frustrating for the workers that handle the metallic connectors. Additionally, at least some metallic connectors require complex casting and finish machining procedures for their production, which can render the metallic connectors relatively costly.
In recent years, there have been significant advancements and a general acceptance of the use of fiber-reinforced polymer materials in structural applications. The American Concrete Institute published a design manual for the use of fiber-reinforced polymer rebars as an alternative to conventional steel reinforcing rebars. Fiber-reinforced polymer materials have the potential to be viable alternatives to conventional steel joint connections because of their material properties that can give them a significant advantage over steel in terms of weight, durability, and corrosion resistance.
Despite best efforts, however, such fiber-reinforced polymer rebars have only been implemented in pre-cast concrete construction practices to a modest extent. A primary reason for the lack of implementation of fiber-reinforced polymer rebars in pre-cast concrete construction practices is that splicing or connecting multiple fiber-reinforced polymer rebars in such applications has proven frustrating or impractical. For example, none of the three typical rebar joinder techniques, (i) welding, (ii) rebar overlap, and (iii) cast-iron connectors, are well suited for use with fiber-reinforced polymer rebars. Welding is unfeasible, rebar overlap can require large overlapping segments which may be wasteful, and cast-iron connectors remain susceptible to corrosion in spite of the corrosion resistant qualities of the fiber-reinforced polymer rebars which frustrates many of the most desirable characteristics of the fiber-reinforced polymer rebars.